A six-storey mixed-use project on Harvey Avenue hit refusal on a dense till layer at 14 metres. The contractor had assumed bedrock would be deeper based on a neighbouring site three blocks away. That assumption nearly doubled the piling budget before our rig arrived. Kelowna's subsurface is like that—glacial lake silts draped over irregular till, with buried channels that can shift bearing strata by several metres across a single city lot. We run the SPT in Kelowna to map those transitions precisely. Each blow count tells us whether we are in compressible silt, dense till, or something in between. For sites near the lake or along Mill Creek, we often pair the SPT with a grain-size analysis to confirm fines content, which directly affects liquefaction susceptibility under the NBCC seismic provisions.
N-value variability across a single Kelowna lot can exceed 30 blows within 3 vertical metres. That is the difference between a spread footing and a deep pile.
Standards that apply
ASTM D1586-18 — Standard Test Method for Standard Penetration Test (SPT) and Split-Barrel Sampling of Soils, ASTM D2488-17e1 — Standard Practice for Description and Identification of Soils (Visual-Manual Procedure), NBCC 2020 — National Building Code of Canada, Part 4, Division B (Seismic Hazard and Foundation Provisions), CSA A23.3:19 — Design of Concrete Structures (reference for foundation concrete), NCEER/NSF (Youd et al., 2001) — Liquefaction Resistance of Soils: Summary Report
Common questions
How much does an SPT borehole cost in Kelowna?
A single SPT borehole to 15 metres depth in the Kelowna area typically ranges from CA$670 to CA$1,060, depending on access conditions, traffic control requirements, and whether the hole is vertical or angled. Deeper holes beyond 25 metres or sites requiring all-terrain rig mobilization in the Upper Mission or lakeshore areas fall at the upper end of that range. Every quote includes the drilling crew, automatic hammer, split spoon sampler, field logging, and the N60-corrected data package.
How deep do you typically drill SPT boreholes in Kelowna?
Most commercial and residential projects in Kelowna require boreholes between 12 and 25 metres. Shallow holes to 10 metres suffice for single-family footings on the benches, while multi-storey buildings along the lakefront or in the downtown core often need 25 metres or more to penetrate through the glaciolacustrine silts and into competent till or bedrock. We determine the target depth based on the structural loads and the proximity to known buried channels mapped in provincial geological surveys.
What is the difference between raw N and N60?
Raw N is the blow count read directly from the field log—the number of hammer drops to drive the split spoon 300 mm after seating. N60 is the same count corrected to a reference energy ratio of 60%, which is the standard assumed in most empirical correlations. Our automatic hammer delivers an energy ratio measured during calibration, and we apply that correction along with factors for rod length, borehole diameter, and overburden pressure. An uncorrected N of 22 in a deep silt layer might become an N60 of 16 after adjustments—that shift changes the bearing capacity output significantly.
Do you need traffic control for SPT drilling on Kelowna streets?
Yes, any borehole located within the municipal right-of-way on streets like Pandosy, Richter, or Gordon requires a street occupancy permit from the City of Kelowna and a traffic management plan. We coordinate the lane closure setup with our subcontractor, who provides certified traffic control personnel, signage, and barricades compliant with the BC Traffic Management Manual. The permitting process typically adds three to five business days to the mobilization timeline.
